1. Field of Invention
This invention relates to a housing mechanism that allows devices to be inserted into the canal of the human ear.
2. Discussion of Prior Art
Hearing aids are the most commonly inserted devices into the human ear. Hearing aids amplify sound to hearing impaired individuals through a microphone/speaker amplification system and are typically contained in housings that are molded to the user's ear, known as earmolds. Earmolds are created by taking an impression of the concha and car canal and then making a plastic shell that matches the user's ear shape. The housing contains the hearing aid electronics as well as a vent tube that connects the users tempanic membrane (ear drum) to the open air. Such a vent tube allows low frequency noise to leave the ear canal: too little venting causes the patient's voice to seem too loud, too much venting can cause acoustic feedback, a process by which amplified sound from the receiver (speaker) travels back to the microphone and is amplified again, resulting in a high pitched whine. Several U.S. patents pertain to methods for creating hearing aid housing devices; relevant prior art includes U.S. Pat. Nos. 4,880,076 (1989), 4,834,927 (1989), 4,962,537 (1990), 5,006,055 (1991), and 5,008,058 (1991).
Hearing aid earmolds are designed to attenuate sound waves to the tempanic membrane. In each of the methods cited above the earmold housing was designed to accommodate hearing aid devices that have both a speaker and a microphone where feedback has been the major design obstacle. In each patent the housing mechanism has been designed to prohibit sound waves from passing through the ear canal to the tempanic membrane, except through the microphone-speaker amplification system. To accomplish the sound wave attenuation, earmolds are often individually molded objects that snugly a user's entire ear canal.
The disadvantage of these approaches is that they limit the application of the earmold to hearing aid or other microphone/speaker amplification systems. Use of earmolds to house devices other than speaker/microphone amplification systems in individuals who have normal hearing capabilities would prohibit sound waves from entering the human ear thereby impair hearing.
Earmolds are also difficult to fit. Because of the need to eliminate feedback by filling the entire ear canal, each earmold must fit an individual user's unique ear shape.
The need to conform exactly to an individual's unique ear canal size and shape, prohibits mass production; the wide variance in human ear canal size and shape and the need to occupy the entire canal prohibits the design of a "one size fits all" earmold.
Another disadvantage of earmolds is the difficulty in creating a fit that secures the device firmly within the ear canal. U.S. Pat. No. 4,880,076 addresses this problem by encasing the device with a compressive foam sleeve. The disadvantage of this housing method is that it requires that the device be "substantially cylindrical," touching all points of the ear canal in the area in which the device sits. Such a method for holding devices necessarily prohibits the passage of sound waves to the tempanic membrane for devices other than speaker/microphone amplification systems.
Earmolds also have difficulty providing a comfortable fit. The feedback problem has limited the type of materials that can be used to create earmolds. Earmolds that are made of Silicone, while soft, flexible and comfortable, do not totally block high frequency wave transmission. Consequently, harder, less comfortable otoplastics have been used in the fabrication of ear molds.